Method of manufacturing a semiconductor device having an enhanced electrode pad structure

ABSTRACT

There are included a semiconductor substrate provided with a desirable element region, an electrode pad formed to come in contact with a surface of the semiconductor substrate or a wiring layer provided on the surface of the semiconductor substrate, a bump formed on a surface of the electrode pad through an intermediate layer, and a resin insulating film formed in at least a peripheral portion of the bump to cover an interface of the bump and the intermediate layer which is exposed to a side surface of the bump.

This application is a divisional of application Ser. No. 10/206,593,filed Jul. 24, 2002, which application is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and a method ofmanufacturing the semiconductor device, and more particularly to thepassivation of the periphery of a bump to be formed on an electrode pad.

2. Description of the Related Art

When a semiconductor device such as a VLSI (very large scaleintegration) is to be manufactured, a passivation structure is veryimportant around a bump formed on an electrode pad, and variousendeavors have been made to enhance a productivity while maintaining areliability.

In recent years, a structure using a polyimide resin for a passivationfilm has variously been proposed. By way of example, as shown in FIG.15, there are formed an electrode pad 2 comprising an aluminum layerformed to come in contact with a surface of a semiconductor substrate 1or a wiring layer provided on the surface of the semiconductorsubstrate, and a metal bump 6 formed in a contact hole H provided on asilicon nitride film 3 for covering the upper layer of the electrode pad2 through a TiW layer to be an intermediate layer 4. The metal bump isformed on a thin metal layer formed by sputtering to be a seed layer 5during plating, and a polyimide resin film 7 to be a passivation film isformed around the metal bump 6.

Such a structure is formed through the following manufacturing process.

First of all, a wiring layer (not shown) and an interlayer insulatingfilm (not shown) are formed on the surface of the silicon substrate 1provided with an element region and a through hole (not shown) is formedby photolithography. Then, the aluminum layer is evaporated and thewiring (not shown) and the electrode pad 2 are subjected to patterningby the photolithography. Thereafter, the silicon nitride film 3 isformed on the upper layer of the wiring and the electrode pad 2 and issubjected to patterning by the photolithography, and a contact hole H isformed in the central part of the electrode pad 2 to cover theperipheral edge of the electrode pad 2 with a silicon nitride film (FIG.16).

As shown in FIG. 17, subsequently, the polyimide resin film 7 to be apassivation film is formed and is subjected to patterning, therebyexposing the electrode pad 2 as shown in FIG. 18.

If the aluminum layer is exposed to a surface, it is apt to be corroded.As shown in FIG. 19, therefore, a titanium tungsten TiW film to be abarrier layer is formed as the intermediate layer 4 on the aluminumlayer by the sputtering method and the metal layer 5 to be a bonding padis then formed.

As shown in FIG. 20, thereafter, the metal layer 5 and the intermediatelayer 4 are subjected to patterning by the photolithography.

Accordingly, it is desirable that the edge of the pad layer 5 iscoincident with that of the polyimide resin film 7. In consideration ofmask precision, there is a problem in that the edges are coincident withdifficulty. On the other hand, there is a problem in that a shortcircuit is apt to be caused if the metal layer 5 and the intermediatelayer 4 get over the passivation film 7. For this reason, the patterningis carried out in consideration of precision in the photolithography.

As shown in FIG. 21, furthermore, the plated layer 6 is formed on themetal layer 5 by electroplating, thereby forming a bump.

As described above, in the method, a clearance is generated between thepolyimide resin film constituting the passivation film and the metallayer 6 constituting the bump, and the TiW surface which is oxidizedeasily is exposed. For this reason, there is a problem in that corrosionis apt to be caused, the passivation effect cannot be obtained well andthe reliability is thereby deteriorated.

In the conventional pad structure, thus, there is a problem in that awater content enters from the clearance between the passivation film andthe bump, the electrode pad such as aluminum is easily corroded and thereliability is thereby maintained with difficulty.

SUMMARY OF THE INVENTION

The invention has been made in consideration of the circumstances andhas an object to provide a semiconductor device comprising a pad havinga passivation structure in which a resistance to a water content is highand a reliability is enhanced.

A first aspect of the invention is directed to a semiconductor devicecomprising a semiconductor substrate provided with a desirable elementregion, an electrode pad formed to come in contact with a surface of thesemiconductor substrate or a wiring layer provided on the surface of thesemiconductor substrate, a bump formed on a surface of the electrode padthrough an intermediate layer, and a resin insulating film formed in atleast a peripheral portion of the bump to cover an interface of the bumpand the intermediate layer which is exposed to a side surface of thebump.

According to such a structure, the resin insulating film is formed tocover the interface of the bump and the intermediate layer which isexposed to the side surface of the bump. Therefore, the electrode padand the intermediate layer which are provided as lower layers are notexposed but covered with the resin insulating film. Consequently, areliability can be enhanced.

The intermediate layer includes a barrier metal layer such as TiW, anadhesion layer or a lower layer constituting a plated substrate. Theinvention is particularly effective in the case in which the layers arecorrosive or are formed of materials which are easily oxidized.

It is desirable that the resin insulating film should be a polyimideresin film.

According to such a structure, it is possible to obtain a pad structurehaving a high reliability which can produce the insulation of thesurface of the peripheral edge in the bump and a passivation effect byusing the polyimide resin film.

It is desirable that the resin insulating film should be formed to havea higher level than the interface.

According to such a structure, it is possible to produce a passivationeffect more reliably.

It is desirable that the intermediate layer should include a titaniumtungsten (TiW) layer.

According to such a structure, there is such a drawback that thetitanium tungsten (TiW) layer is particularly oxidized easily and adeterioration is apt to be caused if the interface is exposed. Accordingto the invention, however, it is possible to easily obtain a bumpstructure having a high reliability.

It is desirable that the bump should be formed of metal.

According to such a structure, it is possible to obtain a semiconductordevice having an excellent bonding property and a high reliability.

It is desirable that the electrode pad should be formed by a metal filmcontaining aluminum.

There is such a drawback that the aluminum layer is particularlyoxidized easily and a deterioration is apt to be caused if the interfaceis exposed. According to such a structure, however, it is possible toeasily obtain a bump structure having a high reliability.

It is desirable that the electrode pad should be a thin copper film.

There is such a drawback that the copper layer is particularly oxidizedeasily and a deterioration is apt to be caused if the interface isexposed. According to such a structure, however, it is possible toeasily obtain a bump structure having a high reliability.

It is desirable that the bump should be formed by a solder ball.

According to such a structure, it is possible to obtain an effectivereliability in the case in which the bump is constituted by the solderball as well as an ordinary columnar projection.

The invention provides a method of manufacturing a semiconductor devicecomprising the steps of forming an electrode pad to come in contact witha surface of a semiconductor substrate provided with a desirable elementregion or a wiring layer provided on the surface of the semiconductorsubstrate, forming an intermediate layer on a surface of the electrodepad, forming a seed layer on a surface of the intermediate layer,forming a resist pattern having a window in a bump formation region byphotolithography, forming a bump on a surface of the seed layer exposedfrom the window of the resist pattern by a plating method, patterningthe intermediate layer and the seed layer by using the bump as a mask,and forming a resin insulating film in at least a peripheral portion ofthe bump to cover an interface of the bump and the intermediate layerover a side surface of the bump.

According to such a structure, the bump is formed and the polyimideresin film is then provided. Therefore, it is possible to well cover theperipheral edge of the bump.

It is desirable that the step of forming a resin insulating filmincludes a step of applying a polyimide resin film.

According to such a structure, the resin insulating film is a polyimideresin film. Therefore, it is possible to obtain a surface structurewhich can easily be formed and has a high passivation effect.

It is desirable that the application should be carried out to have ahigher level than the interface at the step of applying a resininsulating film.

According to such a structure, it is possible to well form a resininsulating film.

It is desirable that the step of forming an intermediate layer shouldinclude a step of forming a titanium tungsten (TiW) layer by asputtering method.

There is such a drawback that the titanium tungsten (TiW) layer isparticularly oxidized easily and a deterioration is apt to be caused ifthe interface is exposed. According to such a structure, however, it ispossible to easily obtain a bump structure having a high reliability.

It is desirable that the step of forming a seed layer should include astep of forming a metal layer by sputtering, and the step of forming abump includes a step of forming a bump comprising a metal layer on theseed layer by electroplating.

According to such a structure, it is possible to form a metal bump moreefficiently.

It is desirable that the step of forming an intermediate layer shouldinclude a step of forming a thin chromium film, the step of forming aseed layer should include a step of sputtering a nickel layer, and thestep of forming a bump should include a step of mounting a solder ballon the nickel layer and fusing an interface of the nickel layer and thesolder ball, a step of removing the resist pattern and patterning theintermediate layer and the seed layer by using the solder ball as amask, and a step of forming a polyimide resin film to cover an interfaceof the solder ball and the intermediate layer.

According to such a structure, it is possible to form the polyimideresin film to well cover the interface of the intermediate layer withoutexposing the same interface when forming the solder ball. Therefore, itis possible to form a solder ball having a high reliability.

The bump indicates a columnar projection or a projection such as asolder ball.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a semiconductor device according to a firstembodiment of the invention,

FIG. 2 is a view showing a process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 3 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 4 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 5 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 6 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 7 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 8 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 9 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 10 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 11 is a view showing the process for manufacturing a semiconductordevice according to the first embodiment of the invention,

FIG. 12 is a view showing a semiconductor device according to a secondembodiment of the invention,

FIG. 13 is a view showing a semiconductor device according to a thirdembodiment of the invention,

FIG. 14 is a view showing a semiconductor device according to a fourthembodiment of the invention,

FIG. 15 is a view showing a semiconductor device according to aconventional example,

FIG. 16 is a view showing a process for manufacturing a semiconductordevice according to the conventional example,

FIG. 17 is a view showing the process for manufacturing a semiconductordevice according to the conventional example,

FIG. 18 is a view showing the process for manufacturing a semiconductordevice according to the conventional example,

FIG. 19 is a view showing the process for manufacturing a semiconductordevice according to the conventional example,

FIG. 20 is a view showing the process for manufacturing a semiconductordevice according to the conventional example, and

FIG. 21 is a view showing the process for manufacturing a semiconductordevice according to the conventional example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a view illustrating a semiconductor device having a padstructure according to a first embodiment of the invention, and FIGS. 2to 11 are views illustrating a process for manufacturing thesemiconductor device according to the first embodiment of the invention.

This structure is characterized in that there are included an electrodepad 2 formed on the surface of a silicon substrate 1 provided with adesirable element region and a bump 6 formed on the surface of theelectrode pad through a titanium tungsten layer to be an intermediatelayer 4 and a resin insulating film formed of a polyimide resin film 7is provided in the peripheral portion of the bump 6 to cover theinterface of the bump 6 and the intermediate layer 4 which is exposed tothe side surface of the bump 6.

The metal layer 5 is a film to be a plated substrate, and the polyimideresin film 7 is formed to have a higher level than the interface of theintermediate layer 4 and the metal layer 5.

Next, description will be given to the process for manufacturing thesemiconductor device according to the first embodiment of the invention.

As shown in FIG. 1, first of all, a semiconductor substrate 1 having afield oxide film (not shown) formed thereon is prepared, and an elementregion such as an MOSFET comprising a polysilicon gate is formed on thefield oxide film and the semiconductor substrate.

Next, an interlayer insulating film (not shown) is formed to cover thesurface. The interlayer insulating film is constituted by PSG (a siliconoxide film doped with phosphorus) or BPSG (a silicon oxide film dopedwith boron and phosphorus), for example. Then, an aluminum wiring havinga thickness of 500 to 1000 nm is formed on the interlayer insulatingfilm. Thus, the aluminum wiring is formed on the semiconductor substrate1 and is then subjected to patterning, thereby forming the electrode pad2.

Thereafter, a silicon nitride film 3 is formed by a sputtering methodand a window is formed to be opened to the electrode pad 2.

As shown in FIG. 2, subsequently, the TiW layer 4 having a thickness of200 nm is formed on the electrode pad 2 and the silicon nitride film 3by the sputtering method and the metal layer having a thickness of 200nm is then formed.

As shown in FIG. 3, thereafter, a resist is applied to form a resistpattern R1 by photolithography.

As shown in FIG. 4, subsequently, a bump is formed on the metal layer 5exposed from the resist pattern R1 by electroplating using the resistpattern R1 as a mask.

As shown in FIG. 5, then, the resist pattern R1 is peeled to expose thebump 6.

As shown in FIG. 6, furthermore, the metal is slightly etched such thatthe metal layer 5 provided on the silicon nitride layer 3 can beremoved, and furthermore, the TiW layer 4 is etched by using the metalbump 6 as a mask.

As shown in FIG. 7, thereafter, the photosensitive polyimide resin 7 isapplied. At this time, the polyimide resin 7 is also formed thinly onthe bump 6.

As shown in FIG. 8, subsequently, exposure is carried out by using apattern formed to remove the polyimide resin 7 provided on the bumpsimultaneously with the formation of a scribe line (not shown). Sincethe polyimide resin 7 has a small thickness on the bump, it does notneed to be removed.

As shown in FIG. 9, then, ashing is carried out to completely remove thephotosensitive polyimide resin 7 provided on the bump 6.

As shown in FIG. 10, furthermore, the polyimide resin is postbaked by aheat treatment at 300° C. for 30 minutes, thereby enhancing the qualityof the film.

As shown in FIG. 11, finally, an O₂ plasma treating step is carried outin order to remove polymer or particles (dust) caused at an etch backstep after the etch back step.

Thus, a semiconductor device having the pad structure shown in FIG. 1 isformed.

According to such a structure, the polyimide resin film 7 is formed tocover the interface of the bump 6 and the TiW layer to be theintermediate layer 4 which is exposed to the side surface of the bump.Therefore, the lower electrode pad 2 and the intermediate layer 4 arenot exposed but are well covered and protected by the polyimide resinfilm so that a pad structure having a long lifetime and a highreliability can be obtained.

Moreover, after the bump is formed, the polyimide resin film 7 isformed. Therefore, it is possible to cover the interface efficiently andwell.

While the description has been given to the case in which the metal bumpis formed in the first embodiment, another layer such as Ti/TiN may beused as the intermediate layer, and furthermore, an adhesion layer suchas a titanium layer or a palladium layer can also be provided.

Furthermore, the pad electrode is not restricted to aluminum but theinvention can also be applied to the case in which the pad electrode isformed of aluminum-silicon (Al—Si), aluminum-silicon-copper (Al—Si—Cu)or copper (Cu).

Next, a second embodiment of the invention will be described.

FIG. 12 is a view showing a semiconductor device according to the secondembodiment of the invention. While the metal bump has been described inthe above-mentioned embodiment, a solder bump will be described in thisexample.

In this example, the electrode pad 2 is formed of aluminum in the samemanner as in the first embodiment, and an intermediate layer to beformed as an upper layer includes a barrier layer 8 a formed by atitanium layer and a nickel layer 8 b to be an adhesion layer, andfurthermore, a solder bump 10 comprising a solder plated layer is formedas an upper layer through a chromium layer 9 to be a seed layer.

The manufacturing process according to the second embodiment is the sameas that of the first embodiment except that it is necessary to set atreating temperature to be low because the melting point of a solder islow.

Also in this case, there is a problem in that a chromium layer is easilyoxidized and corrosion is increased on an interface. According to theembodiment, it is possible to easily obtain a pad structure having ahigh reliability.

Next, a third embodiment of the invention will be described.

FIG. 13 is a view showing a semiconductor device according to the thirdembodiment of the invention. While the bump has been described in thefirst and second embodiments, description will be given to an example inwhich a solder ball is used.

This example is characterized in that a bump to be a columnar projectionis a ball-shaped solder (hereinafter referred to as a solder ball 13),and a Ti layer 11 and a nickel layer 12 are formed, the solder ball 13is then mounted, the interface of the nickel layer and the solder ballis fused, and a polyimide resin film 7 is thereafter formed.

Others are the same as those in the first and second embodiments.

Next, description will be given to a process for manufacturing asemiconductor device having the pad structure.

After an electrode pad 2 and a silicon nitride film 3 to be an upperlayer are formed. In the same manner as in FIG. 2, then, the Ti layer 11having a thickness of 300 nm is formed on the electrode pad 2 and thesilicon nitride film 3 by a sputtering method and the nickel layer 12having a thickness of 200 nm is then formed.

In the same manner as shown in FIG. 3, thereafter, a resist is appliedto form a resist pattern R1 by photolithography.

Subsequently, the solder ball 13 is mounted on the nickel layer 12exposed from the resist pattern R1, a heat treatment is carried out at150° C. and the interface of the nickel layer 12 and the solder ball 13is fused.

In the same manner as shown in FIG. 5, then, the resist pattern R1 ispeeled to expose a solder ball 6.

In the same manner as shown in FIG. 6, furthermore, etching is slightlycarried out such that the Ti layer and the nickel layer which areprovided on the silicon nitride layer 3 can be removed.

In the same manner as shown in FIG. 7, thereafter, the photosensitivepolyimide resin 7 is applied. In the same manner as in the firstembodiment, subsequently, the polyimide resin 7 provided on the solderball 13 is removed so that a pad structure shown in FIG. 13 is formed.

Thus, it is possible to obtain a pad structure having a long lifetimeand a high reliability.

Next, a fourth embodiment of the invention will be described.

FIG. 14 is a view showing a semiconductor device according to a fourthembodiment of the invention. In this example, a semiconductor chip 20 isdirectly connected onto a semiconductor chip 1, while a bonding wire Wis connected to a bump 5 formed on the surface of the semiconductor chip1 and the other end of the bonding wire W is connected to a mountingsubstrate (not shown) such as a lead frame.

Others are the same as those in the first to third embodiments.

According to such a structure, a bonding pad and a bump are formed suchthat side surfaces are covered with a polyimide resin 7 at the same bumpforming step. Therefore, it is possible to form a film having a greatresistance to a water content and a high reliability.

While a lower wiring layer constituted by a field oxide film and analuminum wiring formed thereon has been taken as an example of a lowerlayer in the embodiment, the lower layer is not restricted thereto. Thelower layer in the invention signifies a general layer having aconcavo-convex surface.

As described above, in the invention, the resin insulating film isformed to cover the interface of the bump and the intermediate layerwhich is exposed to the side surface of the bump. Therefore, theelectrode pad and the intermediate layer which are the lower layers arenot exposed but covered with the resin insulating film. Consequently, itis possible to increase a lifetime and to enhance a reliability in asemiconductor device.

According to the method of the invention, moreover, the bump is formedand the resin insulating film is then formed. Therefore, the resininsulating film can be formed in order to well cover the interface ofthe bump and the intermediate layer, and the electrode pad and theintermediate layer which are the lower layers are not exposed butcovered with the resin insulating film. Thus, it is possible to increasea lifetime and to enhance a reliability.

1. A method of manufacturing a semiconductor device comprising the stepsof: forming an electrode pad to come in contact with a desirable elementregion or a wiring layer provided on a surface of a semiconductorsubstrate; forming an insulating layer having a pad opening for exposingat least a portion of a surface of the electrode pad; forming asubstantially uniform intermediate layer directly covering the surfaceof the electrode pad through the pad opening and directly covering aportion of a surface of the insulating layer; forming a resist patternhaving a window in a bump formation region; forming a bump through thewindow of the resist pattern to be in electrical contact with theelectrode pad; removing the resist pattern; etching the intermediatelayer by using the bump having a straight vertical peripheral edge as amask to form a straight vertical peripheral edge; applying a resininsulating film on the insulating layer and on the bump, the resininsulating film being applied in two non-continuous sections, a firstsection of the resin insulating film directly covering the top of thebump and a second section of the resin insulating film directly coveringthe peripheral edge of the intermediate layer and the interface definedby the bump and the intermediate layer, the first section of the resininsulating film being separated from the second section of the resininsulating film by a portion of the bump, the second section of theresin insulating film preventing exposure of the interface, the secondsection of the resin insulating film being applied so that the topsurface of the second section of the resin insulating film is positionedabove the interface between the bump and the intermediate layer andbelow the top surface of the bump; and removing the first section of theresin insulating film by ashing.
 2. The method of manufacturing asemiconductor device according to claim 1, wherein the resin insulatingfilm is formed by applying a polyimide resin.
 3. The method ofmanufacturing a semiconductor device according to claim 2, wherein theresin insulating film is formed to have a higher level than theinterface.
 4. The method of manufacturing a semiconductor deviceaccording to claim 2, wherein the polyimide resin is a photosensitivepolyimide resin and the photosensitive polyimide resin provided on thebump is removed by exposure and ashing.
 5. The method of manufacturing asemiconductor device according to claim 1, wherein the intermediatelayer is formed by forming a TiW layer by a sputtering method.
 6. Themethod of manufacturing a semiconductor device according to claim 5,further comprising forming a seed layer on a surface of the intermediatelayer prior to forming the bump, the step of forming a seed layerincluding a step of forming a metal layer by sputtering, the bump beingformed by forming a metal layer on the seed layer by electroplating. 7.The method of manufacturing a semiconductor device according to claim 6,wherein the step of forming an intermediate layer includes forming athin chromium film, the step of forming a seed layer includes sputteringa nickel layer, and the step of forming a bump includes a step ofmounting a solder ball on the nickel layer and fusing an interface ofthe nickel layer and the solder ball.
 8. The method of manufacturing asemiconductor device according to claim 1, wherein a bonding pad isformed.
 9. The method of manufacturing a semiconductor device accordingto claim 8, further comprising the steps of: connecting the bump ontoanother bump of another substrate directly; and connecting a bondingwire to the bonding pad.